1. Field of the Invention
The present invention relates to a method of performing a treatment such as modification, deposition, or etching on the surface of a solid material and a material treated by the method and, more particularly, to a method of giving liquid repellency to a solid material surface and a material treated by the method.
More specifically, the present invention relates to a method of giving liquid repellency only to the surface of a solid material containing a polymer having on its side chain a single bonding group of a carbon atom and hydrogen atom, by dissociating hydrogen atoms from the solid material surface and at the same time substituting with a carbon fluoride CnFm (n=1, 2, 3, . . . , m=2n, 2n+1) group, and a material treated by the method.
2. Related Background Art
Conventionally, a functional solid material has been so developed that its own physical properties are effectively utilized. However, various physical properties are required in device applications and the like, so it is becoming more and more difficult for any single bulk material to well satisfy the required performance or characteristics. In particular, a fluorine resin is used in various purposes by making use of its characteristic features, such as inertness, water repellency, oil repellency, and resistance to scratching, resulting from low surface energy. For example, a fluorine resin is singly molded into parts and products having diverse shapes or used in the form of a film. Also, a fluorine resin film having one surface which is given hydrophilic nature is used to cover parts having various shapes. Furthermore, a fluorine resin is dissolved in a solvent and used in the form of a coating film. Thus, a fluorine resin is used in a wide variety of applications and hence regarded as one of very useful materials.
Even when this fluorine resin is in the form of a film, however, if a bulk region of a certain size is present in the film, in this bulk region the physical properties unique to the fluorine resin appear. For example, a low hardness decreases the cutting resistance, so the film is readily cut with a knife. In the case of molding, a high glass transition point decreases the flowability, and this makes precision molding difficult to perform. Also, in the case of solvent coating the material is limited to a fluorine polymer which dissolves in a solvent, so the inertness, water repellency, oil repellency, and resistance to scratching do not reach the characteristics of PTFE. Additionally, a high curing temperature restricts the base material that can be coated. Furthermore, the original physical properties of a fluorine resin also pose problems: a large linear expansion coefficient causes deformation in a high-temperature environment, and a high chargeability limits uses in the vicinity of charge carriers.
If, therefore, it is possible, instead of processing a fluorine resin material itself, to add the characteristics of a fluorine resin only to surface region thereof while the original bulk physical characteristics of a base material made of an organic material or organic-inorganic composite material are fully utilized, a wider variety of functions can be achieved.
As this method, Japanese Patent Application Laid-Open No. 6-340759 discloses a method of modifying a plastic material having a Cxe2x80x94H bond by exciting light. That is, this prior art reference describes a method by which, in an atmosphere of a compound or mixture which contains a first atom having a bond energy of 80.6 kcal/mol or more with respect to a hydrogen atom and a second atom or atomic group whose bond energy with respect to the first atom is smaller than the optical energy of the exciting light, the interface between the plastic material and the compound or mixture is directly or indirectly irradiated with ultraviolet light having a photon energy of 80.6 kcal/mol or more. In this manner, the plastic material is dehydrogenated via the first atom and substituted with the second atom or atomic group. As the compound or mixture, fluorine compound examples are presented in Examples 11, 27, and 31.
In the configuration of Japanese Patent Application Laid-Open No. 6-340759 described above, however, variations in the manufacturing conditions produce large variations in the performance of the contact angle owing to the substitution mechanism. Since this requires severe management of the manufacturing conditions, it is difficult to form highly stably surface-treated samples with high yield.
That is, the present inventors conducted experiments by the method described in (Example 2) of Japanese Patent Application Laid-Open No. 6-340759. Consequently, when a sample was irradiated with an ArF laser while being in close contact with an aqueous solution prepared by dissolving 2 g of boric acid (H3BO3) in 50 cc of water, the aqueous boric acid solution absorbed light upon ArF laser irradiation, and this worsened the efficiency of the substitution reaction. Additionally, the thickness of the aqueous boric acid solution sometimes produced variations in the substitution reaction.
Accordingly, the present inventors studied a substitution mechanism for efficiently performing substitution without any variations produced by the thickness of the aqueous boric acid solution or the like, and have found a novel substitution mechanism, thereby deriving a surface treatment stabilization method. In particular, the present inventors have found a method by which a physical property irreversible process logically holds in a method of adding high liquid repellency to the surface of a plastic material having a Cxe2x80x94H bond in its surface layer.
It is an object of the present invention to provide a surface treatment method capable of extending application regions by maintaining both the surface characteristics and bulk characteristics, and capable of achieving both high liquid repellency and high productivity.
To achieve the above object, the present invention provides a surface treatment method of treating the surface of a material to be treated, by irradiating with light the material to be treated and a mediating material in contact with each other, characterized in that the mediating material itself causes substantially no interaction upon irradiation with light, and the surface of the material to be treated is treated by provision of chemical reaction field, in which a substituent of the material to be treated and an atom of atomic group of the mediating material is induced by excitation at the same time, by irradiating with light by using the logical product of the contact interface between the material to be treated and the mediating material and the light irradiation region, thereby causing and progressing bonded state transition.
The method is also characterized in that bond energy by which the substituent induced by excitation from the material to be treated in the chemical reaction field is subjected to captive transition bonding by the atom or atomic group induced by excitation from the mediating material is larger than a larger one of bond energy between the substituent of the material to be treated and a matrix atom and bond energy between the atom or atomic group of the mediating material and the matrix atom.
The method is further characterized in that the light which irradiates the material to be treated and the mediating material has a wavelength having photon energy larger than a larger one of bond energy between the substituent of the material to be treated and a matrix atom and bond energy between the atom or atomic group of the mediating material and the matrix atom.
Also, the present invention for achieving the above object is a method of treating the surface of a material to be treated having a single bonding group of a carbon atom and hydrogen atom on the surface, characterized in that while the material to be treated is in contact with a liquid mediating material which is an aggregate of a polymer having on its main chain an ether bonding group and a carbon fluoride CnFm (n=1, 2, 3, . . . , m=2n or 2n+1) group, the contact interface between the material to be treated and the mediating material is irradiated with ultraviolet radiation having a wavelength of 221.4 to 351.6 nm, thereby substituting a hydrogen atom in the single bonding group of a carbon atom and the hydrogen atom on the surface of the material to be treated with the carbon fluoride group in the mediating material, and modifying the surface of the material to be treated.